It's not really an app, but I did hear that Kovu is currently working on a FeralHeartish game for Facebook, named Feral Tales, but that was quite some time ago, so I'm not sure if it's still being worked on. :I
I would love to have an app for the forums, and/or editing characters though! But like Kijiako and Kiaz said, I don't think it would be possible without Kovu, or at least his permission.